Easily differentiate incidents from incidents created by catalog item forms?

My organization is looking for ways to report more easily on the volume of requests that we're getting as standard incidents compared to the number of requests we're getting through catalog item forms.

Because both of these requests are created as standard incidents and incidents created by catalog items aren't attached to their parent catalog item there doesn't seem to be an easy way to do this.

Going forward, I'm thinking the best solution would be to tag all incidents created by catalog items with a specific tag that we could report on. But that doesn't help us with reporting on historical data.

Is there something that I'm missing here that would work better than my tagging solution?